The long-term objectives of this program are to identify and characterize the behavioral, pharmacological, and environmental factors that affect drug-taking behavior. The more immediate goals are 1) to characterize the pharmacological and behavioral factors acting on narcotic tolerance as it influences various forms of operant behavior with special emphasis upon narcotic self-injection in the rhesus monkey; 2) to determine the effects of narcotic withdrawal induced by narcotic deprivation or by narcotic antagonists upon operant responding controlled by narcotic injections or by other consequences; 3) to study various forms of aversive control of responding by narcotic antagonists in the presence of various degrees of narcotic dependence; and 4) to determine the pharmacological characteristics of narcotic drugs in the production of discriminative stimuli.